1. Field of the Invention
The invention relates to a fuel system for a motor vehicle internal combustion engine.
2. Description of the Related Art
Almost all vehicles have a temporary store for hydrocarbons installed in a tank vent between the fuel tank and the environment. This temporary store typically is an activated carbon filter (ACF) that is regenerated by an air stream and is controlled by the engine electronics. During this process, air is passed via the hydrocarbon-laden particles to produce a hydrocarbon-laden air stream that is carried to the engine. The hydrocarbon-laden air stream coming from the activated carbon filter then is mixed with the combustion air and burned. Vehicles that have hybrid drive often utilize electric operation and hence eliminate a number of purging phases, including phases in the regulation driving profiles. Plug-in hybrids can travel under electric power for long distances, including entire driving cycles of the regulation tests, and therefore eliminate significant proportions of the purging cycle. The activated carbon filter should nevertheless be purged to comply with legal emissions limits.
DE 199 44 388 A1 relates to an apparatus for quickly heating up a pollutant catalyst in a motor vehicle that has an internal combustion engine and a fuel tank. More particularly, fuel constituents that have volatilized out of the fuel supply in the fuel tank are carried by air to the catalyst. The air stream enriched with the volatilized fuel constituents is fed to the catalyst and the volatilized fuel constituents are burned in a burner that is integrated into the inlet side of the catalyst.
JP 2002122046 A discloses a membrane interposed in the tank vent to separate the escaping gas mixture into an air-rich component and a fuel-rich component. The fuel-rich component is liquefied again in a cooler and fed back to the tank.
It is the object of the invention to provide a fuel system that is improved with respect to environmental pollution.